Revealing rare disorders

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Fourteen new developmental disorders have been discovered by a team led by researchers at the Wellcome Trust Sanger Institute, publishing their findings in the journal Nature this month. The Deciphering Developmental Disorders study - the largest of its kind in the world - has been analysing the DNA of thousands of children affected by previously undiagnosed rare genetic conditions, such as intellectual disability, epilepsy, autism or heart defects, along with their parents, in order to uncover the gene faults responsible.

On average, 1 in 300 children born in the UK have a rare developmental disorder caused by a new fault in a gene, adding up to 2,000 children a year in the UK. To find the genes responsible, the team screened all 20,000 or so human genes from more than 4,000 affected UK and Irish families, focusing their attention on new gene faults, or mutations, that crop up randomly as DNA is passed from parents to their child.

By matching up this genetic information with clinical records, the researchers were able to find children with new mutations in genes that had previously been linked to developmental disorders, but also managed to to spot 14 new developmental disorders that had been caused by spontaneous mutations in a child’s DNA and weren’t found in their parents.

Importantly, the study also revealed that older parents have a higher risk of having a child with a developmental disorder due to this kind of new, spontaneous mutation, with the chances rising from 1 in 450 for 20-year-old parents to 1 in 210 for 45-year-old parents. As part of the study, the researchers managed to provide a firm diagnosis for rare conditions affecting over a thousand children and their families - something that is very important for investigating potential treatments, informing the best clinical care, and getting access to additional health and educational support.